'MISSOULA, Mont. -- When Ken Salazar -- then a senator from Colorado, now secretary of the interior -- called the attack on millions of acres of pine forests by the bark beetle the Katrina of the West, he was expressing the common view of the explosive growth of the beetles as an unmitigated disaster.

But not everybody sees it that way. Some environmentalists and scientists support the beetles. While they acknowledge the severity of the problems the beetles are causing, they argue that the insects, which kill only mature trees larger than five inches in diameter, are a natural phenomenon, like forest fires, and play a vital ecological role.

'It's not the end of the forests, and they are not destroyed,' said Diana L. Six, a professor of forest entomology and pathology at the University of Montana here, who has studied the beetle for 16 years, as she walked in a beetle-infected forest near here recently .

'Lodge pole pine evolved to go out with a stand-replacing event, such as fire or beetles, then regenerate really quickly,' she said. 'When they hit 80 or 90 years of age all of a sudden the beetles become a player -- the trees are big enough for the beetles to attack. They reset the clock on the stand.'

Dr. Gregg DeNitto, a forest health specialist with the Forest Service here, said the beetles were not 'an exotic like the emerald ash bore.'"